This invention relates to a conveying roller having an elastomer member disposed on the periphery of a shaft in a uniform thickness in the radial direction, and a method for producing the same.
Hitherto has been known a conveying roller including an elastomer member placed on the periphery of a metal shaft in a uniform thickness in the radial direction. Such a conveying roller having a body member made of elastomer is advantageous in transferring paper in a copying machine, facsimile machine, printing machine, or the like because of flexibility of the elastomer member.
Such conveying rollers have been generally produced by the so-called shaft press-in-fitting method where a shaft coated with an adhesive on the periphery is pressingly inserted in a center hole of a cylindrically formed elastomer body member, or the so-called elastomer winding method where an elastomer material is wound on a shaft coated with an adhesive on the periphery.
The body member always comes into contact with paper or other object, and often comes into contact with chemical material such as developing solution. Accordingly, the body member requires material having high wear resistance and chemical resistance.
In the shaft press-in-fitting method, a cylindrical body member is formed by extrusion molding. The cylindrical body member is formed with a center hole. A shaft is coated with an adhesive, and then is pressed into the center hole of the body member. This method requires skillful and delicate operations. Accordingly, this method is low in the production efficiency while high in the production costs. The same problems are found in the elastomer winding method.
To solve these problems, the so-called injection molding method has been proposed. In the injection molding method, a conveying roller is produced by placing a shaft in a die, and injecting a molten elastomer into a mold space in the die.
As mentioned above, the material for a body member of a conveying roller requires high wear and chemical resistances. However, elastomer having high wear resistance and chemical resistance exhibits a low adhesion. Accordingly, there is a problem that when a conveying roller produced by the injection molding method is placed in operation, the shaft and the elastomer body member slide over each other, impairing the integral rotation of the shaft and the body member.
To increase the adhesion between the shaft and the body member in the injection molding method, there has been proposed addition of a step of applying an adhesive onto a periphery of a shaft placed in a molding die before a molten elastomer is injected into the die. However, this addition makes the production process complicated, and decreases the productivity of conveying roller production.